From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Howells Subject: Re: [RFC] get_write_access()/deny_write_access() without inode->i_lock Date: Mon, 20 Jun 2011 14:20:34 +0100 Message-ID: <22606.1308576034@redhat.com> References: <21839.1308574037@redhat.com> <20110619235147.GQ11521@ZenIV.linux.org.uk> Return-path: In-Reply-To: <21839.1308574037@redhat.com> Sender: linux-fsdevel-owner@vger.kernel.org Cc: dhowells@redhat.com, Al Viro , linux-arch@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, Linus Torvalds List-Id: linux-arch.vger.kernel.org David Howells wrote: > > + for (v = atomic_read(&inode->i_writecount); v >= 0; v = v1) { > > + v1 = atomic_cmpxchg(&inode->i_writecount, v, v + 1); > > + if (likely(v1 == v)) > > + return 0; > > + } > > You don't need to reissue the atomic_read(). atomic_cmpxchg() returns the > current value of the memory location. Just set v to v1 before going round the > loop again. Ah... Never mind - you did that anyway. David From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx1.redhat.com ([209.132.183.28]:47964 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753909Ab1FTNVL (ORCPT ); Mon, 20 Jun 2011 09:21:11 -0400 From: David Howells In-Reply-To: <21839.1308574037@redhat.com> References: <21839.1308574037@redhat.com> <20110619235147.GQ11521@ZenIV.linux.org.uk> Subject: Re: [RFC] get_write_access()/deny_write_access() without inode->i_lock Date: Mon, 20 Jun 2011 14:20:34 +0100 Message-ID: <22606.1308576034@redhat.com> Sender: linux-arch-owner@vger.kernel.org List-ID: Cc: dhowells@redhat.com, Al Viro , linux-arch@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, Linus Torvalds Message-ID: <20110620132034._TJ9zwwSoqUFAuiCpbb2Aqrv3VbRAoRUY5hivCmOQE8@z> David Howells wrote: > > + for (v = atomic_read(&inode->i_writecount); v >= 0; v = v1) { > > + v1 = atomic_cmpxchg(&inode->i_writecount, v, v + 1); > > + if (likely(v1 == v)) > > + return 0; > > + } > > You don't need to reissue the atomic_read(). atomic_cmpxchg() returns the > current value of the memory location. Just set v to v1 before going round the > loop again. Ah... Never mind - you did that anyway. David